Dominance relationships, mating behaviour and scent marking in fox squirrels (Sciurus niger)

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Abstract
Observations (549 h) on fox squirrels (S. niger) marked with either plastic ear tags or collars in a 6.8 ha wood lot (Thompson Woods), Southern Illinois University at Carbondale [Illinois, USA] were studied. Observations (153 h) on a small number of marked squirrels released into another 2.74 ha area reinforced to prevent squirrel escape were also examined. Some squirrels in the 2nd area were eventually sacrificed for histological analysis of lip skin. Fox squirrels inhabit overlapping home ranges during daily feeding and movements rather than defending a territory from which other squirrels are prevented from entering during their foraging and daily movements. Fox squirrels possess a social organization that is described as a linear right hierarchy in situations where there is competition for food and mating rights. Mating behavior in fox squirrels is similar to that described in other tree squirrels in that several males follow a female in estrus and the most dominant male chases off other pursuing males. Fox squirrels facewipe, i.e., rub the sides of their face alternately on some substrate several times in succession; the facewiping is postulated to be a type of scent marking. Prevalence of facewiping in Thompson Woods'' fox squirrels was correlated with age and dominance which would be expected if facewiping as a type of scent marking was an expression of dominance. The most dominant squirrel in the enclosure population had the largest sebaceous and mucus glands in the skin around the mouth, and all fox squirrels possess a lip plate on the inner surface of the upper lip which might be used in deposition of scent.